Tropical Storm Barry, which formed off Mexico's Gulf Coast on Wednesday, has prompted Mexican authorities to ready hundreds of shelters. The U.S. National Hurricane Center in Miami said the Atlantic hurricane season's second tropical storm was drenching areas in its path with up to 10 inches of rain in some places, raising the threat of flash floods.

View full sizeTropical Storm Barry is expected to hit the shoreline of Veracruz, Mexico, on Thursday morning.NOAA

At 4 a.m., Barry was located at 19.6 degrees North and 96.2 degrees West, or about 30 miles east northeast of Veracruz, Mexico. Barry is expected to make landfall near that port city Thursday morning.

A tropical storm warning is in effect for Punta El Lagarto to Barra De Nautla, Mexico, along the southwest coast of the Gulf of Mexico.

Forecasters declared the formation of the second named storm of the year at about 1:40 p.m. Wednesday, after satellite images and data from an Air Force reconnaissance plane found sustained tropical force winds in the Barry's center.

"There is a chance for Barry to strengthen slightly just before landfall during the next 12 to 18 hours," said Senior Hurricane Specialist Lixion Avila in a 4 p.m. forecast discussion message. The official forecast calls for maximum winds of 45 mph as it moves ashore.

View full sizeNOAA's GOES-13 satellite captured this image of Tropical Storm Barry in the southwestern Gulf of Mexico soon after it was declared a tropical storm Wednesday afternoon.NOAA

"Rapid weakening is anticipated after the center moves inland, but rains will continue," he warned. The storm was moving westward at 5 to 10 knots on Wednesday and that motion will continue, with a slowing of its forward speed as it approaches the shore.

"Once inland, and the center becomes disrupted by the high terrain, the remnant circulation will likely continue westward over the state of Veracruz until dissipation," Avila said. The forecast calls for the storm to dissipate by 1 p.m. on Friday.

Avila warned residents and visitors to central Mexico not to focus on the track of the eye of Barry, because rainfall within the broader storm system is likely to be its biggest threat.

"It is important to emphasize that regardless of the exact track and whether the cyclone strengthens, the main threat will be heavy rainfall, which could cause significant flooding over a large portion of southern Mexico, primarily in the state of Veracruz during the next couple of days," he said.

Tropical storm force winds extend outward up to 70 miles from Barry's center, primarily to the east. Barry is expected to produce total rainfall amounts of 3 to 5 inches, with some locations seeing up to 10 inches. These rains could cause life-threatening flooding and mudslides, especially in mountainous areas.